On Friday, September 20, we released 500 Hypena opulenta caterpillars in Ottawa to combat dog-strangling vine. Dog-strangling vine (DSV), Vincetoxicum rossicum, also known as pale swallow-wort, is a highly invasive plant introduced from Ukraine that has invaded many natural areas in Ontario, especially around Toronto and Ottawa, and the northeast US. Once it invades an area, DSV forms thick monocultures and is extremely difficult to eradicate. It is toxic to mammals and to monarch butterflies, which sometimes make the mistake of laying eggs on DSV instead of on their usual host, milkweed. Like its host plant, Hypena opulenta is native to Ukraine. Before it could be released as a control agent, it underwent stringent testing to make sure it would not feed on other plants, especially DSV’s relatives in the milkweed family, some of which are endangered. Once the panel of expert reviewers was convinced that the risk of Hypena attacking other plants was vanishingly small, the release was approved. The first release of 500 larvae will test whether the agent can successfully overwinter here in Ottawa. Additional releases are planned for next spring. The caterpillars we released will soon pupate in the litter around the plants and emerge next spring as adult moths. Hopefully next spring we will see lots of feeding damage on DSV leaves! Links to the host-specificity testing conducted at the University of Rhode Island by students in Richard Casagrande’s lab:http://cels.uri.edu/news/nSwallowWort.aspxhttp://digitalcommons.uri.edu/dissertations/AAI1497502/http://www.dartmouth.edu/~asweed/Research/Welcome_files/Hazlehurst-2012.pdf